Friction Stir Welded Monolithic Aircraft Structure and Method

ABSTRACT

A method of forming a monolithic aircraft structure having multiple aerodynamic surfaces includes forming a body component to have a body skin defining a body skin outer surface, and a body side wall integrally formed with the body skin and defining a body mating surface, the body skin outer surface providing a first aerodynamic surface. A cover component is formed to have a cover mating surface and a cover outer surface opposite the cover mating surface, the cover outer surface defining a second aerodynamic surface. The body component is positioned relative to the cover component so that the body mating surface engages the cover mating surface. At least portions of the cover mating surface are friction stir welded to the body mating surface to form friction stir welded joints between the body component and the cover component.

TECHNICAL FIELD

The present disclosure generally relates to monolithic aircraftstructures and methods and, more specifically, to friction stir weldedmonolithic aircraft structures having multiple aerodynamic surfaces andmethods of forming such structures.

BACKGROUND

Structures used on aircraft may have aerodynamic surfaces (i.e., controlsurfaces) that are exposed to ambient air during flight. Thesestructures may be formed of two or more components that are joinedtogether. An aircraft spoiler, for example, typically includes multiplecomponents that are fastened or bonded together to form the completespoiler. One configuration of a spoiler is a monolithic, machined uppercomponent with a lower cover attached for aerodynamic purposes. Theupper component has an outer surface facing away from the aircraft wingthat is continuously exposed to ambient air during flight. The coveralso has an outer surface that typically overlies a flap of the aircraftwhen in a neutral position, but may move to a deployed position in whichthe outer surface of the cover is spaced from the flap. Traditionalmethods of joining such components, such as bolting, require additionallabor and expense, add to the weight of the aircraft, and introduceaerodynamic drag.

SUMMARY

In accordance with one example, a method is provided of forming amonolithic aircraft structure having multiple aerodynamic surfaces. Themethod includes forming a body component to have a body skin defining abody skin outer surface, and a body side wall integrally formed with thebody skin and defining a body mating surface, the body skin outersurface providing a first aerodynamic surface. A cover component isformed to have a cover mating surface and a cover outer surface oppositethe cover mating surface, the cover outer surface defining a secondaerodynamic surface. The body component is positioned relative to thecover component so that the body mating surface engages the cover matingsurface. At least portions of the cover mating surface are friction stirwelded to the body mating surface to form friction stir welded jointsbetween the body component and the cover component.

In accordance with another example, a monolithic aircraft structureincludes a body component having a body skin with a body skin outersurface defining a first aerodynamic surface, and a body side wallintegrally formed with the body skin and defining a body mating surface.A cover component has a cover mating surface and a cover outer surfaceopposite the cover mating surface, wherein the cover mating surface isshaped conformally with the body mating surface, and wherein the coverouter surface defines a second aerodynamic surface. At least onefriction stir welded joint extends through the cover mating surface ofthe cover component and into the body mating surface of the bodycomponent.

In accordance with yet another example, an aircraft spoiler includes abody component having a body skin with a body skin outer surfacedefining a first aerodynamic surface, a body side wall integrally formedwith the body skin and defining a body mating surface, the body sidewall including generally triangular first and second side panels joinedby a rear panel, and at least one stiffener integrally formed with thebody skin and the body side wall and disposed between the first andsecond side panels, the at least one stiffener defining a stiffenermating surface. A cover component has a cover mating surface and a coverouter surface opposite the cover mating surface, wherein the covermating surface is shaped conformally with the body mating surface andthe stiffener mating surface, the cover outer surface defining a secondaerodynamic surface. At least one friction stir welded joint extendsthrough the cover mating surface of the cover component and into thebody mating surface of the body component, and at least one additionalfriction stir welded joint extending through the cover mating surface ofthe cover component and into the stiffener mating surface of the atleast one stiffener.

In another aspect of the disclosure that may be combined with any ofthese aspects, the body component further comprises at least onestiffener integrally formed with the body skin and the body side walland defining a stiffener mating surface, and the method furthercomprising friction stir welding at least a portion of the stiffenermating surface to the cover mating surface to form an additionalfriction stir welded joint between the body component and the covercomponent.

In another aspect of the disclosure that may be combined with any ofthese aspects, the at least one stiffener comprises a boss forming aportion of the stiffener mating surface, and in which the boss isfriction stir welded to the cover mating surface to form the additionalfriction stir welded joint.

In another aspect of the disclosure that may be combined with any ofthese aspects, forming the cover component further comprises forming asocket sized to receive a portion of the boss.

In another aspect of the disclosure that may be combined with any ofthese aspects, friction stir welding at least a portion of the stiffenermating surface to the cover mating surface comprises friction stirwelding continuously along an entirety of the stiffener mating surfaceto the cover mating surface.

In another aspect of the disclosure that may be combined with any ofthese aspects, the method further comprises, subsequent to friction stirwelding at least portions of the cover mating surface to the body matingsurface to form the friction stir welded joints, heat treating the bodycomponent and the cover component.

In another aspect of the disclosure that may be combined with any ofthese aspects, the method further comprises, subsequent to friction stirwelding at least portions of the cover mating surface to the body matingsurface to form the friction stir welded joints, performingnon-destructive inspection of the friction stir welded joints betweenthe body component and the cover component.

In another aspect of the disclosure that may be combined with any ofthese aspects, the method further comprises, subsequent to friction stirwelding at least portions of the cover mating surface to the body matingsurface to form the friction stir welded joints, applying at least onesurface treatment selected from a group of surface treatments consistingof anodizing, primer coating, and topcoating to the body skin outersurface and the cover outer surface.

In another aspect of the disclosure that may be combined with any ofthese aspects, forming the body component comprises machining the bodycomponent from a block of aluminum alloy material.

In another aspect of the disclosure that may be combined with any ofthese aspects, forming the cover component comprises machining the covercomponent from a sheet of aluminum alloy material.

In another aspect of the disclosure that may be combined with any ofthese aspects, forming the body component comprises forming a spoilerbody, and forming the cover component comprises forming a spoiler cover.

In another aspect of the disclosure that may be combined with any ofthese aspects, forming the spoiler body further includes formingfittings integrally with the body skin and body side wall.

In another aspect of the disclosure that may be combined with any ofthese aspects, the body component further comprises at least onestiffener integrally formed with the body skin and the body side walland defining a stiffener mating surface, and further comprising at leastone additional friction stir welded joint extending through the covermating surface of the cover component and into the stiffener matingsurface of the at least one stiffener.

In another aspect of the disclosure that may be combined with any ofthese aspects, the at least one stiffener comprises a boss forming aportion of the stiffener mating surface, and in which the at least oneadditional friction stir welded joint is formed between the cover matingsurface of the cover component and the boss of the at least onestiffener.

In another aspect of the disclosure that may be combined with any ofthese aspects, the cover component further includes a socket sized toreceive a portion of the boss.

In another aspect of the disclosure that may be combined with any ofthese aspects, the at least one additional friction stir welded jointcomprises a continuous friction stir welded joint extending along anentirety of the stiffener mating surface

These and other aspects and features will become more readily apparentupon reading the following detailed description when taken inconjunction with the accompanying drawings. In addition, althoughvarious features are disclosed in relation to specific examples, it isunderstood that the various features may be combined with each other, orused alone, with any of the various examples without departing from thescope of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an example aircraft that may be used toimplement example methods and apparatus disclosed herein.

FIG. 2 is a side elevation view, in cross-section, of a wing of theaircraft taken along line 2-2 of FIG. 1.

FIG. 3 is an exploded view, in perspective, of a spoiler used on thewing of FIG. 2, showing a body component and a cover component.

FIG. 4 is a side elevation view, in cross-section, of a friction stirwelded joint formed in the spoiler of FIG. 3.

FIG. 5 is a side elevation view, in cross-section, of an additionalfriction stir welded joint formed in the spoiler of FIG. 3.

FIG. 6 is an exploded view, in perspective, of an alternative example ofa spoiler used on the wing of FIG. 2 showing alternative body and covercomponents.

FIG. 7 is a side elevation view, in cross-section, of a friction stirwelded joint formed in the spoiler of FIG. 6.

FIG. 8 is a schematic flowchart illustrating a method of forming amonolithic aircraft structure having multiple aerodynamic surfaces,according to the present disclosure.

It should be understood that the drawings are not necessarily drawn toscale and that the disclosed examples are sometimes illustratedschematically. It is to be further appreciated that the followingdetailed description is merely exemplary in nature and is not intendedto limit the disclosure or the application and uses thereof. Hence,although the present disclosure is, for convenience of explanation,depicted and described as certain illustrative examples, it will beappreciated that it can be implemented in various other types ofexamples and in various other systems and environments.

DETAILED DESCRIPTION

The following detailed description is of the best currently contemplatedmodes of carrying out the disclosure. The description is not to be takenin a limiting sense, but is made merely for the purpose of illustratingthe general principles of the disclosure, since the scope of thedisclosure is best defined by the appended claims.

Monolithic aircraft structures having multiple aerodynamic surfaces, andmethods for forming such structures, are disclosed herein having reducedweight and aerodynamic drag. An exemplary aircraft structure includes abody component defining a first aerodynamic surface, and a covercomponent defining a second aerodynamic surface. The body component andcover component are joined by friction stir welding to form a monolithicstructure. The friction stir weld may be continuous or intermittentabout a perimeter of the body and cover components. Additional frictionstir welds may be used between the cover component and optionalstiffeners provided with the body component, and again may be continuousor intermittent along the stiffeners. Joining the body and covercomponents using friction stir welds avoids the assembly expense,weight, and aerodynamic drag associated with the use of fasteners.

As used in the examples disclosed herein, the terms “aerodynamicsurface” and “control surface” are used interchangeably to refer to acomponent and/or a surface that defines an aerodynamic flow surface usedto control flight and/or navigation of an aircraft or other vehiclebased on fluid flow (e.g., airflow during movement and/or flight). Forexample, the term “control surface” may encompass a surface of anaerodynamic structure (e.g., a top surface of a flap) or an activelydisplaced and/or rotated component such as a flap, spoiler or aileron,for example. As used herein, the term “a chord length” refers to alength along a flow path or airflow direction along a direction oftravel of an aircraft, unless described otherwise. As used herein theterm “angle from horizontal” of an aircraft refers to an angle and/orrelative angles corresponding to a reference plane defined as an angleaway from a neutral position of a control surface, whereas the term“horizontal” in this context refers to the neutral position and/or angleof the control surface. As used herein, the term “upper surface” refersto a top surface (e.g., a wing top surface) of an aircraft on oppositeside from landing gear of the aircraft while the term “lower surface”refers to a bottom surface side (e.g., a wing bottom surface) thatcorresponds to the landing gear.

FIG. 1 illustrates an example aircraft 100 in which the examplesdisclosed herein may be implemented. In the illustrated example, theaircraft 100 includes stabilizers 102 and wings 104 attached to afuselage 106. The wings 104 of the illustrated example have controlsurfaces (e.g., flaps, ailerons, spoilers, tabs, etc.) 108, some ofwhich are located at a trailing edge of the wings 104 and may bedisplaced or adjusted (e.g., angled, etc.) to provide lift duringtakeoff, landing and/or flight maneuvers. In some examples, the controlsurfaces 108 are operated (i.e., displaced) independently of oneanother. The control surfaces 108 include leading edge flaps 109,leading edge slats 110, upper surface spoilers (e.g., flight spoilers,ground spoilers, upper surface spoilers, etc.) 112, and trailing edgeflaps (e.g., rotatable flaps) 114. The control surfaces 108 of theillustrated example also include ailerons 118 and flaperons 120. In thisexample, the stabilizers 102 include elevators 122 and a rudder 123. Thewings 104 also define upper and lower surfaces (e.g., upper and lowersides, upper and lower aerodynamic surfaces, etc.) 124, 126,respectively.

To control flight of the aircraft 100, the upper surface spoilers 112 ofthe illustrated example alter the lift and drag of the aircraft 100. Therotatable flaps 114 alter the lift and pitch of the aircraft 100. Theflaperons 120 and the ailerons 118 of the illustrated example alter theroll of the aircraft 100. In this example, the edge slats 110 alter thelift of the aircraft 100. The control surfaces 108 of the illustratedexample also play a role in controlling the speed of the aircraft 100.For example, the upper surface spoilers 112 may be used for braking ofthe aircraft 100. Any of the control surfaces 108 of the illustratedexample may be independently moved (e.g., deflected) to control the loaddistribution in different directions over the wing 104, therebydirecting movement of the aircraft 100.

The examples described herein may be applied to control surfacesassociated with any of the stabilizers 102, the wings 104 and/or anyother exterior or outboard structure (e.g., a horizontal stabilizer, awing strut, an engine strut, a canard stabilizer, etc.) of the aircraft100. In particular, the wings 104 and/or the stabilizers 102 may havecontrol surfaces 108 that can be adjusted to maneuver the aircraft 100and/or control a speed of the aircraft 100, for example. Additionally oralternatively, in some examples, the fuselage 106 has control surfaces,which may be deflected, to alter the flight maneuvering characteristicsduring cruise and/or takeoff of the aircraft 100.

FIG. 2 illustrates a monolithic aircraft structure in the form of aspoiler 200 provided on the wing 104 of the aircraft 100. The spoiler200 may have a neutral position, as shown in FIG. 2, in which thespoiler overlies a wing 104 of the aircraft 100. The spoiler 200,however, may be rotated from the neutral position to alter anaerodynamic characteristic of the aircraft, such as lift, in acontrolled manner. The spoiler 200 includes fittings, such as lugs 202,204, with lug 202 configured for attachment to an actuator 206. Theactuator 206 may operate to move the spoiler 200 from the neutralposition.

FIG. 3 provides an exploded view of the spoiler 200. The spoiler 200generally includes a body component 210 and a cover component 212. Thebody component 210 generally defines the overall shape of the spoiler200, and includes a body skin 214 having a body skin outer surface 216.The body skin outer surface 216 is directly exposed to ambient airduring flight of the aircraft 100, and therefore provides a firstaerodynamic surface of the spoiler 200. That is, a position of the bodyskin outer surface 216 may be controlled to affect one or moreaerodynamic characteristics of the wing 104, such as magnitude of lift.The body component 210 further includes a body side wall 218 integrallyformed with and extending away from the body skin 214. In theillustrated example, the body side wall 218 includes generallytriangular first and second side panels 220, 222 joined by a rear panel224. The body skin 214 and integral body side wall 218 define a cavity225. While the shape of the side panels 220, 222 in the illustratedexample give the spoiler 200 an overall shape resembling a triangularwedge, it will be appreciated that the side panels 220, 222 may haveother shapes to give the spoiler 200, or other monolithic aircraftcomponent, a different overall shape. Furthermore, the body side wall218 may include additional panels, such as a front panel, to furtheralter the overall shape of the spoiler 200.

The body side wall 218 further defines a body mating surface 226 tofacilitate joining of the body component 210 with the cover component212. In the example illustrated at FIG. 3, the body mating surface 226extends around a perimeter of a bottom side 228 of the body component210. The body mating surface 226 may be substantially planar as shown toconform to the cover component 212, as discussed more fully below.Accordingly, in the illustrated example, the body mating surface 226appears as a relatively narrow strip extending around a perimeter of thebottom side 228 of the body component 210.

The body component 210 may further include stiffeners 230 disposedbetween the side panels 220, 222 of the body side wall 218, thereby toimprove the structural strength of the assembled aircraft structure. Asbest shown in FIG. 3, the body component 210 includes six stiffeners 230that are integrally formed with the body skin 214 and the body side wall218, although a different number of stiffeners 230 may be used withoutdeparting from the scope of this disclosure. The stiffeners 230 dividethe cavity 225 into sub-cavities 227. Each stiffener 230 may have ashape that conforms to a cross-sectional shape of the body component210, such as a triangular shape as illustrated. At least one of thestiffeners 230 may further have a top edge defining a stiffener matingsurface 232. The stiffener mating surface 232 may be disposed in thesame plane as the body mating surface 226 of the body side wall 218. Insome examples, the body component 210 may be formed from a block ofmaterial, such as aluminum alloy, that is machined to form the body skin214, body side wall 218, lugs 202, 204, and stiffeners 230.

The cover component 212 is shaped to closely overlie the bottom side 228of the body component 210, thereby to enclose the cavity 225. In theillustrated example showing the spoiler 200, the cover component 212 isformed as a sheet having a substantially uniform thickness. The covercomponent 212 includes a cover mating surface 240 which is oriented toface toward the body component 210 during assembly, and a cover outersurface 242 opposite the cover mating surface 240 and defining a secondaerodynamic surface of the spoiler 200. The cover mating surface 240 isshaped to conform to the body mating surface 226 of the body component210. Additionally, the cover mating surface 240 may be further shaped toconform to the stiffener mating surface 232, if provided. In someexamples, the cover component 212 is machined from a sheet of aluminumalloy.

The body component 210 and cover component 212 are joined together by atleast one friction stir welded joint 250 to form a monolithic aircraftstructure. As best shown in FIG. 4, the friction stir welded joint 250may be formed by a friction stir welding tool 252 having a pin 254.During the friction stir welding process, the pin 254 of the frictionstir welding tool 252 is rotated and forced through the cover component212 and into the body mating surface 226 of the body component 210. Heatand pressure generated by the friction stir welding tool 252mechanically intermixes portions of the body component 210 and the covercomponent 212 to form the friction stir welded joint 250. In theillustrated example, the friction stir welded joint 250 extends throughthe cover component 212 and portions of the body component 210. Thefriction stir welded joint 250 may extend continuously along the entirebody mating surface 226, or multiple friction stir welded joints 250 maybe formed intermittently along the body mating surface 226.

The body component 210 and cover component 212 also may be joined by atleast one additional friction stir welded joint 260, to more securelyjoin the body component 210 to the cover component 212 and furtherimprove the structural integrity of the resulting, monolithic spoilerstructure. More specifically, the additional friction stir welded joint260 may be formed through the cover mating surface 240 of the covercomponent 212 and the stiffener mating surface 232 provided on at leastone of the stiffeners 230 formed integrally with the body component 210,as best shown in FIG. 5.

An alternative example of a spoiler 200′ is illustrated at FIGS. 6 and7. The spoiler 200′ is similar to the spoiler 200 described above, butincludes a body component 210′ having stiffeners 230′ with bosses 234′,and a cover component 212′ having a cover mating surface 240′ formedwith sockets 244′ sized to receive the bosses 234′, as described ingreater detail below.

As best shown at FIG. 6, the stiffeners 230′ of the body component 210′include localized portions of increased thickness having a generallycylindrical shape, thereby to form bosses 234′. Each stiffener 230′ isshown having two bosses 234′, however a different number of bosses 234′may be provided on each stiffener 230′. Furthermore, while eachstiffener 230′ is shown having the same number of bosses 234′, it willbe appreciated that the stiffeners 230′ may have different numbers ofbosses 234′ or may be provided without any boss 234′. Furthermore, thebosses 234′ may project slightly above the stiffener 230′ in which it isformed.

The cover component 212′ may include the sockets 244′ to positivelyposition the cover component 212′ relative to the body component 210′during assembly. Accordingly, as best shown in FIG. 6, the covercomponent 212′ includes a socket 244′ associated with each boss 234′provided with the body component 210′. When the cover component 212′ isplaced on top of the body component 210′ as shown in FIG. 7, frictionstir welded joints 260′ may be formed through each socket 244′ andassociated boss 234′. Accordingly, the bosses 234′ provide additionalmaterial with which to form the friction stir welded joints 260′,thereby more securely joining the cover component 212′ to the bodycomponent 210′.

FIG. 8 schematically illustrates a method 300 of forming a monolithicaircraft structure having multiple aerodynamic surfaces. The methodbegins at block 302 by forming a body component 210 having integral bodyskin 214 having a body skin outer surface 216 defining a firstaerodynamic surface, body side wall 218, and, optionally, stiffeners230, lugs 202, 204, and bosses 234′. The body component 210 may bemachined from a plate of aluminum alloy. At block 304, a cover component212 is formed having to have a cover mating surface 240 and a coverouter surface 242 defining a second aerodynamic surface. The covercomponent 212 may be formed from a sheet of aluminum alloy. The method300 may optionally include a dimensional inspection of the bodycomponent 210 and the cover component 212 at block 306, to ensure thatthe components meet the desired size specifications.

At block 308, the method may continue by positioning the body component210 relative to the cover component 212 so that the body mating surface226 engages the cover mating surface 240. Continuing at block 310, themethod includes friction stir welding at least portions of the covermating surface 240 to the body mating surface 226 to form friction stirwelded joints 250 between the body component 210 and the cover component212, thereby to form a monolithic aircraft structure. Optionally, atblock 312, the method may include forming additional friction stirwelded joints 260 between the cover mating surface 240 and at least onestiffener 230, if provided. It will be appreciated that, in someexamples, the friction stir welded joints 250 and the additionalfriction stir welded joints 260 are formed by inserting the frictionstir welding tool 252 through the aerodynamic surface defined by thecover outer surface 242 of the cover component 212. While conventionalwelding or other joining processes may introduce drag, and thereforetheir use on an aerodynamic surface are typically avoided, formation ofthe friction stir welded joints 250 and additional friction stir weldedjoints 260 leaves a relatively smooth outer surface, thereby minimizingdrag introduced by the component joining process. Furthermore, thefriction stir welding process causes portions of the body component 210and cover component 212 to be intermixed, resulting in a morepermanently joined, monolithic structure.

The method 300 may include several optional steps after the frictionstir welded joints 250 and the additional friction stir welded joints260 are formed. For example, at block 314, the assembled body component210 and cover component 212 are heat treated to improve structuralintegrity of the spoiler 200. At block 316, non-destructive inspectionof the friction stir welded joints 250 and the additional friction stirwelded joints 260 is performed to ensure that the spoiler 200 isstructurally sound. Finally, at block 318, at least one surfacetreatment selected from a group of surface treatments consisting ofanodizing, primer coating, and topcoating is applied to the body skinouter surface 216 and the cover outer surface 242, thereby to improveaerodynamic qualities of the spoiler 200, such as reducing drag over theaerodynamic surfaces.

All references, including publications, patent applications, andpatents, cited herein are hereby incorporated by reference. All methodsdescribed herein can be performed in any suitable order unless otherwiseindicated herein or otherwise clearly contradicted by context. The useof any and all examples, or exemplary language (e.g., “such as”)provided herein, is intended to illuminate the disclosed subject matterand does not pose a limitation on the scope of the claims. Any statementherein as to the nature or benefits of the exemplary examples is notintended to be limiting, and the appended claims should not be deemed tobe limited by such statements. More generally, no language in thespecification should be construed as indicating any non-claimed elementas being essential to the practice of the claimed subject matter. Thescope of the claims includes all modifications and equivalents of thesubject matter recited therein as permitted by applicable law. Moreover,any combination of the above-described elements in all possiblevariations thereof is encompassed by the claims unless otherwiseindicated herein or otherwise clearly contradicted by context.Additionally, aspects of the different examples can be combined with orsubstituted for one another. Finally, the description herein of anyreference or patent, even if identified as “prior,” is not intended toconstitute a concession that such reference or patent is available asprior art against the present disclosure.

What is claimed is:
 1. A method of forming a monolithic aircraftstructure having multiple aerodynamic surfaces, the method comprising:forming a body component to have a body skin defining a body skin outersurface, and a body side wall integrally formed with the body skin anddefining a body mating surface, the body skin outer surface providing afirst aerodynamic surface; forming a cover component to have a covermating surface and a cover outer surface opposite the cover matingsurface, the cover outer surface defining a second aerodynamic surface;positioning the body component relative to the cover component so thatthe body mating surface engages the cover mating surface; and frictionstir welding at least portions of the cover mating surface to the bodymating surface to form friction stir welded joints between the bodycomponent and the cover component.
 2. The method of claim 1, in whichthe body component further comprises at least one stiffener integrallyformed with the body skin and the body side wall and defining astiffener mating surface, and the method further comprising frictionstir welding at least a portion of the stiffener mating surface to thecover mating surface to form an additional friction stir welded jointbetween the body component and the cover component.
 3. The method ofclaim 2, in which the at least one stiffener comprises a boss forming aportion of the stiffener mating surface, and in which the boss isfriction stir welded to the cover mating surface to form the additionalfriction stir welded joint.
 4. The method of claim 3, in which formingthe cover component further comprises forming a socket sized to receivea portion of the boss.
 5. The method of claim 2, in which friction stirwelding at least a portion of the stiffener mating surface to the covermating surface comprises friction stir welding continuously along anentirety of the stiffener mating surface to the cover mating surface. 6.The method of claim 1, further comprising, subsequent to friction stirwelding at least portions of the cover mating surface to the body matingsurface to form the friction stir welded joints, heat treating the bodycomponent and the cover component.
 7. The method of claim 1, furthercomprising, subsequent to friction stir welding at least portions of thecover mating surface to the body mating surface to form the frictionstir welded joints, performing non-destructive inspection of thefriction stir welded joints between the body component and the covercomponent.
 8. The method of claim 1, further comprising, subsequent tofriction stir welding at least portions of the cover mating surface tothe body mating surface to form the friction stir welded joints,applying at least one surface treatment selected from a group of surfacetreatments consisting of anodizing, primer coating, and topcoating tothe body skin outer surface and the cover outer surface.
 9. The methodof claim 1, in which forming the body component comprises machining thebody component from a block of aluminum alloy material.
 10. The methodof claim 1, in which forming the cover component comprises machining thecover component from a sheet of aluminum alloy material.
 11. The methodof claim 1, in which: forming the body component comprises forming aspoiler body; and forming the cover component comprises forming aspoiler cover.
 12. The method of claim 11, in which forming the spoilerbody further includes forming fittings integrally with the body skin andbody side wall.
 13. A monolithic aircraft structure, comprising: a bodycomponent including: a body skin having a body skin outer surfacedefining a first aerodynamic surface; and a body side wall integrallyformed with the body skin and defining a body mating surface; a covercomponent having a cover mating surface and a cover outer surfaceopposite the cover mating surface, wherein the cover mating surface isshaped conformally with the body mating surface, and wherein the coverouter surface defines a second aerodynamic surface; and at least onefriction stir welded joint extending through the cover mating surface ofthe cover component and into the body mating surface of the bodycomponent.
 14. The monolithic aircraft structure of claim 13, in whichthe body component further comprises at least one stiffener integrallyformed with the body skin and the body side wall and defining astiffener mating surface, and further comprising at least one additionalfriction stir welded joint extending through the cover mating surface ofthe cover component and into the stiffener mating surface of the atleast one stiffener.
 15. The monolithic aircraft structure of claim 14,in which the at least one stiffener comprises a boss forming a portionof the stiffener mating surface, and in which the at least oneadditional friction stir welded joint is formed between the cover matingsurface of the cover component and the boss of the at least onestiffener.
 16. The monolithic aircraft structure of claim 15, in whichthe cover component further includes a socket sized to receive a portionof the boss.
 17. The monolithic aircraft structure of claim 14, in whichthe at least one additional friction stir welded joint comprises acontinuous friction stir welded joint extending along an entirety of thestiffener mating surface.
 18. An aircraft spoiler, comprising: a bodycomponent including: a body skin having a body skin outer surfacedefining a first aerodynamic surface; a body side wall integrally formedwith the body skin and defining a body mating surface, the body sidewall including generally triangular first and second side panels joinedby a rear panel; and at least one stiffener integrally formed with thebody skin and the body side wall and disposed between the first andsecond side panels, the at least one stiffener defining a stiffenermating surface; a cover component having a cover mating surface and acover outer surface opposite the cover mating surface, wherein the covermating surface is shaped conformally with the body mating surface andthe stiffener mating surface, the cover outer surface defining a secondaerodynamic surface; at least one friction stir welded joint extendingthrough the cover mating surface of the cover component and into thebody mating surface of the body component; and at least one additionalfriction stir welded joint extending through the cover mating surface ofthe cover component and into the stiffener mating surface of the atleast one stiffener.
 19. The aircraft spoiler of claim 18, in which theat least one stiffener comprises a boss forming a portion of thestiffener mating surface, and in which the at least one additionalfriction stir welded joint is formed between the cover mating surface ofthe cover component and the boss of the at least one stiffener.
 20. Theaircraft spoiler of claim 19, in which the cover component furtherincludes a socket sized to receive a portion of the boss.